The present invention generally relates to brake systems and more particularly relates to a device for brake pressure control.
A device of this general type is described in DE 35 45 566 A1. It comprises, among other elements, a travel simulator comprised of spring elements, and a pressure supply device with a rubber-diaphragm type pressure reservoir. With rubber diaphragms of this type, gas is gradually diffusing into the brake fluid. Upon failure of the pressure supply device the entire brake system may become unfit for use because the volume of the master brake cylinder is not sufficient to compress the gas contained in the pressure fluid. When the brake system is intact, the gas which entered into the brake circuits cannot be detected by the driver because the pedal feeling remains unchanged due to the employment of the travel simulator.
Thus, an object of the present invention is to improve the reliability in operation of the prior art device, to achieve brake force boosting which is optimal in terms of pedal comfort, and to permit a comfortable brake intervention independent of the driver by way of an electric or electronic control device. Another objective is to permit monitoring the reliability in operation of the brake system by electrically or electronically determining the bleeding condition.
In the device according to the present invention, the entire pressure fluid which is necessary for the braking operation is made available by the pressure supply device by way of application of the brake pistons. The brake pistons are used as a blocking means between the pressure fluid in the actual braking cycle and the possibly gas-containing pressure fluid in the pressure supply device. Extensive tests have shown that a direct application of the brake cylinders out of the pressure supply device is allowable only for short-term ABS brake operations because otherwise the brake effect may be impaired due to insufficient bleeding.
Another advantage of the device of the present invention is that the signals of the measuring data emitters can be used to check the bleeding condition of the brake system. A combined evaluation of the measuring data, compared to stored nominal values or characteristic curves or fields of characteristic curves, permits inferring the condition of the system and triggering an alarm signal, if necessary.
Consequently, the device of the present invention not only permits better preventing the ingress of gas into the actual braking cycle but also achieving an automatic monitoring of the bleeding condition and failure signalling.